This invention relates to a mechanism for automatically winding a wristwatch from motion of the wearer's wrist, and more particularly to an improved motion conversion device for the mechanism.
Automatic or "self-winding"wristwatches, in which the mainspring is wound by the movement of an off-center weight on a rotor, need a motion conversion device to convert the to-and-fro rotor motion into a unidirectional rotary motion to wind the mainspring. The self-wind mechanism also needs reduction gearing to multiply the force of the weak repetitive movements of the rotor into sufficient force to wind the main spring.
Various types of devices for converting oscillating rotor motion to unidirectional rotary motion have been employed in the prior art. These tend to be complicated and delicate, as well as difficult to assemble in view of the small size of the parts.
An example of an automatic winding mechanism for a watch is seen in U.S. Pat No. 3,104,517 issued Sept. 24, 1963 to the applicant and assigned to the aplicant's assignee, which is fully incorporated herein by reference. In this patent, the motion conversion device comprises a heart-shaped cam and spring loaded pawls pivotably mounted on a lever which cooperate to actuate a ratchet wheel. The ractchet wheel winds the mainspring barrel through planetary reduction gears.
Another type of motion conversion device is seen in U.S. Pat. No. 2,696,073 issued to G. Langel on Dec. 7, 1954, in which an eccentric crank portion on the oscillating rotor staff imparts rectilinear motion to a spring loaded double hairpin ratchet spring driving the ratchet wheel. Both the aforementioned U.S. Pat. Nos. 3,104,517 and 2,696,073 require several parts and are difficult to assemble.
Other patents illustrative of automatic winding devices for wristwatches are U.S. Pat. No. 2,928,231 issued Mar. 15, 1960 to Murrle; U.S. Pat. No. 2,645,894 issued July 21, 1953 to Huguenin; U.S. Pat No. 2,744,413 issued May 8, 1956 to Schneider; U.S. Pat. No. 2,807,133 issued Sept. 24, 1957 to Maire; U.S. Pat. No. 2,874,532 issued Feb. 24, 1959 to Baier; and U.S. Pat. No. 2,942,486 issued June 28, 1960 to Beguin.
It would be desirable to have an automatic winding mechanism for wristwatches which would permit easy access to the self-winding mechanism, easy removal of the rotor and associated parts for servicing, and easy reassembly without need for adjustment. Further, since the rotor is actuated by motion of the wearer's arm, it must be rugged and resistant to sudden shocks.
Accordingly, one object of the present invention is to provide an improved automatic winding mechanism for wristwatches which employs a minimum of parts and is easy to assemble.
Another object of the invention is to provide an improved device for converting oscillating motion of the rotor in a self-winding watch to unidirectional rotation of the winding pinion, using an improved rocking arm.